If you were to mistake the Rhinoceros Hornbill for some sort of prehistoric dinosaur, you wouldn't be alone. This big, mostly black bird has more in common with dinosaurs than just feathers and fierce, staring eyes. As one of the largest hornbills, the Rhinoceros Hornbill also has one of the largest and most impressive casques -- a feature they share with hadrosaurids from more than 60 million years ago.
A casque is the large head ornamentation that looks almost like a second bill atop a hornbill's head, and is what inspired the Rhinoceros Hornbill's common name. Both male and female hornbills have casques, so while the male's is often just a little bit bigger, that isn't a fool-proof way to tell the sexes apart. (The best way is to look at their eyes: males have mahogany red eyes, while the female's eyes are white.) The hornbill's casque is formed from the same material as your fingernails (keratin), and can take up to six years to fully develop. Also like your fingernails, the Rhinoceros Hornbill's beak and casque are naturally white. Throughout the bird's lifetime, it rubs its beak and casque against an oil gland under its tail to gradually produce the glossy red-yellow-orange color that's so striking in adult birds.
The Rhinoceros Hornbill's casque isn't just about looking handsome, though. The structure is mostly hollow, and is thought to amplify the hornbill's calls so they can be heard all throughout the Indonesian rainforest. This feature has led paleontologists to believe that maybe harosaurs used their fancy head crests in the same way. So when you hear a Rhinoceros Hornbill's echoing honk from somewhere out of sight, you might just be hearing the voice of this great bird's inner dinosaur.